Diffuse Reflectance Spectrometer Research Articles

In vivo reflectance measurement of optical properties, blood oxygenation and motexafin lutetium uptake in canine large bowels, kidneys and prostates

Motexafin lutetium (MLu) is a second-generation photosensitizer for photodynamic therapy (PDT) of cancer. We have developed and applied a diffuse optical reflectance spectrometer for in vivo measurement of MLu uptake, optical properties, haemoglobin concentration and haemoglobin oxygen saturation in normal canine large bowels, kidneys and prostates.The probe consists of a broadband fibre-optic-coupled light source and detector fibres placed at various distances from the source fibre to collect reflected light. An analysis based on the diffusion approximation of the photon transport equation was used to recover tissue optical properties from the reflectance measurements. The instrumentation and analysis methods were validated using measurements from homogeneous, highly scattering phantoms with known MLu concentrations. The same techniques were then used to estimate chromophore concentrations of normal canine large bowels, kidneys and prostates.We estimated (mean (standard deviation)) total haemoglobin concentrations of 119 (25), 340 (92) and 51 (11) μM in the large bowels, kidneys and prostates of four dogs, respectively; tissue blood oxygen saturations in these same organs were 75 (15), 76 (21) and 74 (16) per cent, respectively. Tissue MLu concentrations (mg l−1) were estimated from data taken 3.5 h after injection of a 2 mg kg−1 injected dose; data from three dogs gave concentrations of 2.4 (0.4) in large bowels, 6.8 (1.3) in kidneys and 2.2 (1.1) in prostates. The reduced scattering coefficients, μs′, estimated for large bowels, kidneys and prostates at 730 nm were, respectively: 10.1 (1.3), 19.6 (4.0) and 12.7 (0.6) cm−1.We observed significant variability in MLu uptake, tissue scattering and haemoglobin concentration between organs and even between the same organ in different dogs. This class of in situ optical property measurement may be desirable to individualize PDT drug and light delivery.

Rapid, specific determination of iodine and iodide by combined solid-phase extraction/diffuse reflectance spectroscopy.

A new, rapid methodology for trace analysis using solid-phase extraction is described. The two-step methodology is based on the concentration of an analyte onto a membrane disk and on the determination by diffuse reflectance spectroscopy of the amount of analyte extracted on the disk surface. This method, which is adaptable to a wide range of analytes, has been used for monitoring ppm levels of iodine and iodide in spacecraft water. Iodine is used as a biocide in spacecraft water. For these determinations, a water sample is passed through a membrane disk by means of a 10-mL syringe that is attached to a disk holder assembly. The disk, which is a polystyrene-divinylbenzene composite, is impregnated with poly(vinylpyrrolidone) (PVP), which exhaustively concentrates iodine as a yellow iodine-PVP complex. The amount of concentrated iodine is then determined in only 2 s by using a hand-held diffuse reflectance spectrometer by comparing the result with a calibration curve based on the Kubelka-Munk function. The same general procedure can be used to determine iodide levels after its facile and exhaustive oxidation to iodine by peroxymonosulfate (i.e., Oxone reagent). For samples containing both analytes, a two-step procedure can be used in which the iodide concentration is calculated from the difference in iodine levels before and after treatment of the sample with peroxymonosulfate. With this methodology, iodine and iodide levels in the 0.1-5.0 ppm range can be determined with a total workup time of approximately 60 s with a RSD of approximately 6%.

Noninvasive Determination of Hemoglobin and Hematocrit Using a Temperature-Controlled Localized Reflectance Tissue Photometer

We performed visible/near-infrared optical measurements on the forearm of human subjects. We conducted four studies: one study using a commercial diffuse reflectance spectrometer, and three studies using a breadboard temperature-controlled localized reflectance tissue photometer. Calibration relationships were established between skin reflectance signal and either the reference blood hemoglobin (Hb) concentration or the hematocrit values (Hct). Prediction results were expressed as the prediction correlation coefficient (rp) and the standard error for cross-validation prediction (CV-SEP). Using diffuse reflectance measurement, rp = 0.8, CV-SEP = 0.9 g/dL for Hb and rp = 0.7, CV-SEP = 3.3% for Hct (n = 40). In a localized reflectance study involving calculating the absorption and scattering coefficients and including effect of change of skin temperature in the calibration model, the best prediction results were rp = 0.9, CV-SEP = 0.8 g/dL for Hb and rp = 0.8, CV-SEP = 3% for Hct (n = 26). In a second localized reflectance study on a population having diverse skin colors at 34°C, the optimal model led to rp = 0.8, CV-SEP = 0.9 g/dL for Hb and rp = 0.9, CV-SEP = 2.1% for Hct (n = 28) using the localized reflectance values without deducing the absorption and scattering coefficients. Improvement in the correlation was more noticeable for Hct than for the case of Hb. The photometer was used to screen prospective blood donors with low Hb concentration. It was possible to predict anemic subjects in the limited prospective blood donor population.

Design and testing of a white-light, steady-state diffuse reflectance spectrometer for determination of optical properties of highly scattering systems

We present a steady-state radially resolved diffuse reflectance spectrometer capable of measuring the absorption and transport scattering spectra of tissue-simulating phantoms over an adjustable 170-nm wavelength interval in the visible and near infrared. Measurements in a variety of phantoms are demonstrated over the relevant range of tissue optical properties, and the accuracy of the instrument is found to be approximately 10% in both scattering and absorption. Monte Carlo simulations designed to test the accuracy of the instrument are presented that support the experimental findings.

Vapor-Phase Beckmann Rearrangement over Silica-Supported Tantalum Oxide Catalysts

Silica-supported tantalum oxide catalysts (Ta oxide/SiO2 (ALK)), prepared by chemical reaction between tantalum alkoxide and surface hydroxyl groups of SiO2, exhibited high catalytic efficiency for the vapor phase Beckmann rearrangement of cyclohexanone oxime to caprolactam. The oxime conversion reached 96.5%, and the selectivity for caprolactam was 97.5% at 573 K. The effects of precursors of tantalum oxide, physical properties of catalyst carriers, and preparation conditions were studied, and the factors in catalytic efficiency were discussed. SiO2 was the best carrier for the reaction among SiO2, Al2O3, TiO2, MgO, and SiO2-Al2O3. The pore structure of silica carriers, especially the high ratio (>90%) of the pore volume for fine pores with diameters from 4 to 200 nm to total pore volume was effective. Ta2O5/SiO2 (IMP) catalyst, prepared by impregnation of silica with an aqueous TaCl5 solution and hydrated tantalum oxide (Ta2O5 · nH2O) were less active and less selective. A large number of acid sites of intermediate strength, measured by NH3-TPD method, existed on Ta2O5/SiO2 (ALK) and were effective for the Beckmann rearrangement. On the contrary, strong acid sites appeared on Ta2O5/SiO2 (IMP). The difference in the acid property and catalytic performance between Ta2O5/SiO2 (ALK) and Ta2O5/SiO2 (IMP) was assumed to be related to the difference in morphology of tantalum oxide that was observed by SEM and EPMA. Good initial activity and high selectivity for caprolactam were observed over boron oxide supported on alumina catalyst. However, the oxime conversion declined significantly. Although the NH3-TPD profile of B2O3/Al2O3 catalyst was similar to that of Ta2O5/SiO2 (ALK), tantalum oxide of Ta2O5/SiO2 (ALK) was more stable than boron oxide of B2O3/Al2O3 in the course of reaction. The reaction between tantalum alkoxide vapor and the surface hydroxyl groups of SiO2 was observed by FTIR diffuse reflectance spectrometer. A new hydroxyl group appeared on Ta2O5/SiO2 (ALK) catalyst. The unique acid property and catalytic performance of Ta2O5/SiO2 (ALK) were discussed in connection with the new hydroxyl group.

Infrared spectra of platinum-impregnated V 2O 5 powders on hydrogen insertion

Infrared spectra were measured in the wavenumber range 400–4000 cm −1 during the heating of platinum-impregnated V 2O 5 powders from room temperature to 250 °C in hydrogen gas (0.58 MPa) or on H x V 2O 5 ( x=0–3.27) by a Fourier transform IR diffuse reflectance spectrometer. It is found that the O-H stretching vibration mode at 3372 cm −1 becomes enlarged as the temperature or hydrogen concentration is increased, whereas the V-O stretching vibration modes tend to disappear, and that a new IR band assigned to the O-H bending mode appears at 920 cm −1; no clear evidence for the existence of V-H hydride bonds is detected. These spectral changes suggest a hydrogen-induced amorphization through bond rearrangements. In fact, the Bragg reflection lines due to V 2O 5 tend to be invisible with increasing amount of absorbed hydrogen. The hydrogen-induced amorphization in V 2O 5 is discussed in some detail in the light of information about the structural changes in V 2O 5 on hydrogen insertion and after heat treatment.

Effect of alkaline carbonate on the dissociation of the CO bond in the methanation over [formula omitted] catalyst

By using a pulse microreactor in conjunction with an emissionless infrared diffuse reflectance spectrometer, the dynamics of adsorbed CO as well as produced CH 4 were measured and effects of alkaline carbonate were investigated for the surface reaction of methanation on Ru Al 2O 3 catalyst. Alkaline carbonate added to the Ru catalyst decreased the rate constant for CO bond dissociation, but scarcely affected the hydrogenation of the surface carbon species produced. Alkaline carbonate shifted the infrared absorption band of adsorbed CO to a lower frequency as a result of the increase in electron density in the Ru metal. It is concluded that the effect of alkaline carbonate is an electronic one whereby the CO bond dissociation in the methanation is influenced. The suppressing effect of alkaline carbonate is discussed in terms of a proposed mechanism for the CO bond dissociation which takes into account the electronic effect.

Rate constants of surface reactions in methanation over ruthenium/alumina catalyst as determined by pulse surface reaction rate analysis

By use of a new PSRA (pulse surface reaction rate analysis) apparatus equipped with an emissionless infrared diffuse reflectance spectrometer (EDR) and a flame ionization detector (FID), the dynamics of both adsorbed CO and produced CH/sub 4/ were simultaneously measured in the CO hydrogenation over Ru/Al/sub 2/O/sub 3/ catalyst. When a CO pulse was introduced to the catalyst via the H/sub 2/ at temperatures above 405 K, an IR absorption band assignable to a linearly adsorbed CO appeared at 2040 cm/sup -1/. At the same time an FID response of CH/sub 4/ quickly increased. It was found that k/sub CH/sub x// is more than 50 times larger than k/sub CO/, indicating that on the Ru/Al/sub 2/O/sub 3/ catalyst the formation of (CH/sub x/)/sub ad/ from adsorbed CO is much slower than its hydrogenation to CH/sub 4/. Furthermore, an H/sub 2/-D/sub 2/ inverse isotope effect was observed for k/sub CO/, suggesting that hydrogen atoms play an important role in the C-O bond dissociation in the CO hydrogenation. A mechanism of the C-O bond dissociation was also discussed on the basis of these results for k/sub CO/. 7 references, 17 figures, 2 tables.

Surface reaction rate of hydrogenation of adsorbed carbon monoxide as examined by an emissionless infrared diffuse reflectance spectrometer

The behaviors of adsorbed CO species during the methanation of CO on supported metal catalysts were examined by using an EDR (emissionless infrared diffuse reflectance spectrometer). Major adsorbed species observed under steady-state CO-H/sub 2/ reaction were adsorbed CO and surface formate, and appreciable absorption could not be observed in C-H and O-H regions. The rate constants of disappearance of adsorbed species on 0.5% Pd/Al/sub 2/O/sub 3/ under the reaction conditions were also measured from the transient responses of IR spectra. The intensities of the bands due to surface formate did not change with time, showing that the surface formate is not an intermediate. The rate constants of disappearance of adsorbed CO (linear CO and bridge CO) were essentially identical with each other and were in good agreement with the rate constant of CH/sub 4/ formation measured by PSRA (pulse surface reaction rate analysis). These data indicate that the rate-determining step in the methanation of CO is the C-O bond dissociation of adsorbed species and the hydrogenation of the adsorbed carbon species proceeds rapidly. 8 figures, 1 table.

Design and construction of an emissionless infrared diffuse reflectance spectrometer

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTDesign and construction of an emissionless infrared diffuse reflectance spectrometerMiki. Niwa, Tadashi. Hattori, Mamoru. Takahasi, Kenji. Shirai, Michio. Watanabe, and Yuichi. MurakamiCite this: Anal. Chem. 1979, 51, 1, 46–49Publication Date (Print):January 1, 1979Publication History Published online1 May 2002Published inissue 1 January 1979https://doi.org/10.1021/ac50037a019RIGHTS & PERMISSIONSArticle Views81Altmetric-Citations21LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (384 KB) Get e-Alerts Get e-Alerts

EMISSIONLESS DIFFUSE REFLECTANCE IR SPECTROSCOPY AT HIGH TEMPERATURE

Abstract New diffuse reflectance spectrometer in the infrared region was made to eliminate the emission spectrum, and emissionless spectra of powder CaCO3 were measured in the temperature range from room temperature to 450°C.